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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b8eda7e6577sm488931866b.30.2026.02.10.02.00.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Feb 2026 02:00:16 -0800 (PST) Message-ID: <6f506caf-4910-4d29-86c6-4dd57aa559a6@oss.qualcomm.com> Date: Tue, 10 Feb 2026 11:00:14 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 6/9] usb: misc: qcom_eud: add host mode coordination To: Elson Serrao , Greg Kroah-Hartman , Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Souradeep Chowdhury Cc: linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260126233830.2193816-1-elson.serrao@oss.qualcomm.com> <20260126233830.2193816-7-elson.serrao@oss.qualcomm.com> <0fd2cff2-176e-419d-9e11-a98150266fee@oss.qualcomm.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <0fd2cff2-176e-419d-9e11-a98150266fee@oss.qualcomm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-GUID: bbwc9nz5rBDxOVw7leEU8du3wITRwRPk X-Proofpoint-ORIG-GUID: bbwc9nz5rBDxOVw7leEU8du3wITRwRPk X-Authority-Analysis: v=2.4 cv=YrIChoYX c=1 sm=1 tr=0 ts=698b01b4 cx=c_pps a=qKBjSQ1v91RyAK45QCPf5w==:117 a=FpWmc02/iXfjRdCD7H54yg==:17 a=IkcTkHD0fZMA:10 a=HzLeVaNsDn8A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=IqIWAEJlBQ2RpOI2llkA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=NFOGd7dJGGMPyQGDc5-O:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjEwMDA4MyBTYWx0ZWRfX2MuqucR0l3IZ ZAEFvdH7ly6NN0CydEgvRw625UwDf6s0ekpetGJuEWkUNaLAnHWNjhyoRkdX6wNbbndu5xhPBte cFscEE6rvH2HGCSNbCLFgW8eT4gTH4pw7ZiPOf20k+9TP4L60BdoAECH3ReCT3w6s9tW6ETbKo7 UhvHfcPfGfxnubE5QwA4RQHyPs8RxMaQADjaQIjX10+9hcOmEylwZsQhGPSStB0IJKChKXhSYnJ zPiXA2pd3GXNYKYAuUOo1PPAO8RBPIIN7xXs1ng3e0Jf7mCVYgCvxtpWqNfcQrOHSTV08+Ciizg yd8BZXtiWXNDzPpOFMSVUjvJfDv7Pd8e+/gnVbFB90C9tsMbkoLBckk02SKruOcMYRlpprKqCcU XHNntmL2098NrLuc5jObaE4we0wp8VSTLw2HG7YHX3AVm0/PbLuiYn/NfUoat1zbV/zEQLDthrK A+bjgrcmoAURS8swYbA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-09_01,2026-02-09_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 bulkscore=0 adultscore=0 clxscore=1015 impostorscore=0 lowpriorityscore=0 priorityscore=1501 phishscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602100083 On 2/9/26 6:37 PM, Elson Serrao wrote: > > > On 2/4/2026 5:29 AM, Konrad Dybcio wrote: >> On 1/27/26 12:38 AM, Elson Serrao wrote: >>> EUD functions by presenting itself as a USB device to the host PC for >>> debugging, making it incompatible in USB host mode configurations. >>> Enabling EUD, when in host mode can also cause the USB controller to >>> misbehave as the EUD hub can only have one upstream facing port. >> >> Perhaps that's a silly idea, but would the device itself see >> the debug hub, being able to essentially self-debug in a way? >> > > This isn’t supported by the current hardware topology. > > When EUD is enabled, it enumerates as a USB device to an external host via its > upstream-facing port, while the SoC USB controller sits behind the hub’s > downstream-facing port. As a result, the controller cannot enumerate or > interact with the EUD device itself, and host mode is mutually exclusive with > EUD debug on this path. OK, I see. Thanks Konrad